Complexes In Silicon Research Articles

Bistability-Mediated Carrier Recombination at Light-Induced Boron-Oxygen Complexes in Silicon

A first-principles study of the BO2 complex in B-doped Czochralski Si reveals a defect-bistability-mediated carrier recombination mechanism, which contrasts with the standard fixed-level Shockley-Read-Hall model of recombination. An O2 dimer distant from B causes only weak carrier recombination, which nevertheless drives O2 diffusion under light to form the BO2 complex. Although BO2 and O2 produce nearly identical defect levels in the band gap, the recombination at BO2 is substantially faster than at O2 because the charge state of the latter inhibits the hole capture step of recombination.

The As2V complex in silicon: Band-gap levels, migration and annealing

In this study, we used n+p mesa diodes where the highly arsenic doped n+ top layer was grown by molecular-beam epitaxy on top of a 5-μm thick p-type layer grown by chemical-vapour deposition. The diodes were irradiated with 2MeV electrons at room temperature and the resulting defects in the p-type region were studied by Laplace and standard deep-level transient spectroscopy. A new defect with an apparent energy position of 0.20eV above the valence band is shown to migrate from the n+ top layer into the p-type material where it is observed by DLTS. An annealing study shows that this defect grows in at ∼400K and disappears at ∼460K. We argue that this defect is the As2V complex, and that it is formed in the top layer when negatively charged AsV pairs, which are generated in the n+ top layer by the electron irradiation, migrate and react with the abundant and positively charged As donors. Once formed, the As2V complex diffuses into the p-type material.

Bistability and electrical activity of the vacancy-dioxygen complex in silicon

The methods of infrared absorption. Hall effect, and deep-level transient spectroscopy are used to study the complexes that consist of a vacancy and two oxygen atoms (the vacancy-dioxygen complexes, VO2) in irradiated n-Si crystals with various levels of doping. The previously observed bistability of VO2 is confirmed and evidence is provided for electrical activity of this defect in the metastable configuration VO*2. It is established that the defect with this configuration features an acceptor level located at E C − 0.06 eV. It is shown that the absorption bands at 967 and 1023 cm−1 are caused by the negatively charged VO*2 state, while the bands peaking at 928 and 1004 cm−1 correspond to the neutral charge state of the defect.

Nitrogen-doped Czochralski silicon treated in rapid thermal process

Nitrogen is one of the most important elements in Czochralski (CZ) silicon used in ultra-large scale integrity circuits (ULSI). In last decades, nitrogen-doped Czochralski (NCZ) silicon, which has been widely applied in microelectronic industry, has attracted much attention. In this presentation, the behavior of NCZ silicon treated in rapid thermal process (RTP) has been reviewed. The influence of RTP on oxygen precipitation, bulk microdefects, denuded zone and nitrogen and oxygen complexes in NCZ silicon has been investigated. The interaction of nitrogen with oxygen and vacancies in CZ silicon during RTP is also discussed.

Electron capture cross-section of Au–Fe complex in silicon

A deep level transient spectroscopy technique is applied to study the capture cross-section of an iron–gold complex. The thermal ionization energy obtained from emission rate data is found to be Ec −0.36 eV. The Au–Fe complex is a single defect having a capture cross-section of 2.48×10−16 cm2 for electrons which is independent of temperature.

Atomic scale simulations of arsenic–vacancy complexes in germanium and silicon

Atomistic simulation is used to study vacancy-assisted defect interactions in germanium (Ge). The structures and relative energies of a series of different arsenic (As)–vacancy complexes in Ge are considered. In all cases the calculations use a plane-wave basis set and pseudo-potentials within the generalized gradient approximation (GGA) of density functional theory (DFT). The technique is also used to model equivalent defects in silicon (Si) and predictions show good correspondence to the results of previous experimental and modelling studies. The calculations for Ge also indicate important differences in the binding energies of several As–vacancy and related complexes in Ge compared to Si.

Annealing behaviors of vacancy in varied neutron irradiated Czochralski silicon

The difference of annealing behaviors of vacancy-oxygen complex (VO) in varied dose neutron irradiated Czochralski silicon: (S1 5×10 17 n/cm 3 and S2 1.07×10 19 n/cm 3) were studied. The results show that the VO is one of the main defects formed in neutron irradiated Czochralski silicon (CZ-Si). In this defect, oxygen atom shares a vacancy, it is bonded to two silicon neighbors. Annealed at 200 °C, divacancies are trapped by interstitial oxygen(O i) to form V 2O (840 cm −1). With the decrease of the 829 cm −1 (VO) three infrared absorption bands at 825 cm −1 (V 2O 2), 834 cm −1 (V 2O 3) and 840 cm −1 (V 2O) will rise after annealed at temperature range of 200–500 °C. After annealed at 450–500 °C the main absorption bands in S1 sample are 834 cm −1, 825 cm −1 and 889 cm −1 (VO 2), in S2 is 825 cm −1. Annealing of A-center in varied neutron irradiated CZ-Si is suggested to consist of two processes. The first is due to trapping of VO by O i in low dose neutron irradiated CZ-Si (S1) and the second is due to capture the wandering vacancy by VO, etc, in high dose neutron irradiated CZ-Si (S2), the VO 2 plays an important role in the annealing of A-center. With the increase of the irradiation dose, the annealing behavior of A-center is changed.

Electrical activity of thePtH2complex in silicon: High-resolution Laplace deep-level transient spectroscopy and uniaxial-stress technique

High-resolution Laplace deep-level spectroscopy combined with the uniaxial stress technique has been used to study stress-energy piezospectroscopic tensor components of the platinum-dihydrogen complex in silicon. The effect of stress on the defect has been observed either as the stress-induced Laplace deep-level transient spectroscopy peak splitting (which is interpreted as an effect of stress on the defect ionization process) or as a stress-induced defect alignment. The latter has been observed for both defect charge states, i.e., singly and doubly negative. The kinetics of the alignment process allowed us to conclude that the energy barrier separating equivalent defect configurations is $1\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, which means that the complex does not reorient below the room temperature. The character of the lattice relaxation derived from the piezospectroscopic characteristics of the complex suggests that in $\mathrm{Pt}{\mathrm{H}}_{2}$ the hydrogen atoms are not directly bonded to platinum.

Simulation of the response of divacancy and As–V complex in silicon to external elastic strains

In this work we apply the plane wave ab initio code VASP for the estimation of the components of dipole tensors for the divacancy and the As–V pair, in silicon. Different charge states of defects are considered, and correlations of the defect dipole tensors and defect relaxation pattern with the defect charge are discussed.

Formation of hydrogen-boron complexes in boron-doped silicon treated with a high concentration of hydrogen atoms

The formation of hydrogen (H) related complexes and their effect on boron (B) dopant were investigated in B-ion implanted and annealed silicon (Si) substrates treated with a high concentration of H. Isotope shifts by replacement of $^{10}\mathrm{B}$ with $^{11}\mathrm{B}$ were observed for some H-related Raman peaks, but not for other peaks. This shows proof of the formation of B-H complexes in which H directly bonds to B in Si. This is an experimental result concerning the formation of B-H complexes with H bonded primarily to B. Electrical resistivity measurements showed that the B acceptors are passivated via the formation of the observed B-H complexes, as well as the well-known passivation center in B-doped Si; namely, the H-B passivation center.

Formation and Properties of Iron-Phosphorus and Iron-Phosphorus-Hydrogen Complexes in Silicon

Hitherto unreported ESR signal, labeled TU10, was detected after annealing of electronirradiated silicon samples doped with phosphorus, iron and hydrogen. The ESR spectrum corresponds to a complex having monoclinic-I symmetry and S = 3/2 spin-state. Hyperfine structure of the TU10 spectrum suggests participation of two nucleus with spin I = 1/2 and 100% abundance in the core of the related defect. Doping of samples with hydrogen-deuterium mixture revealed presence of one hydrogen atom in the complex. The second nucleus with I = 1/2 is apparently a phosphorus atom. Presence of single iron atom was verified by doping with iron heaving modified isotope content. An intensity of the previously reported TU6 signal, related to iron-phosphorus complex, was significantly suppressed in hydrogen-doped samples.

The Effect of Thermal Treatments on the Annealing Behaviour of Oxygen-Vacancy Complexes in Irradiated Carbon-Doped Silicon

Cz-grown, carbon-doped silicon samples were irradiated by fast neutrons. We investigated the annealing behaviour of oxygen-related defects, by infrared spectroscopy. We studied the reaction channels leading to the formation of various VmOn defects and in particular the VOn defects formed by the accumulation of oxygen atoms and vacancies in the initially produced by the irradiation VO defects, as the annealing temperature ramps upwards. We mainly focused on bands appearing in the spectra above 450 oC. A band at 1005 cm-1 is found to be the convolution of two bands at 1004 and 1009 cm-1. The latter band has the same thermal stability with the 983 cm-1 of the VO4 defect and therefore is also attributed to this defect. The former band has the same thermal stability with three other bands at 965, 1034 and 1048 cm-1. These four bands may be attributed to VOn (n=5,6) defects, although other VmOn complexes are also potential candidates. Furthermore, we found that pre-treatments of the samples at 1000 oC, with or without the application of high hydrostatic pressure lead to an increase in the concentration of the VO2, VO3 and generally VOn defects in comparison with that of the untreated samples.

Structure and dynamics of the diarsenic complex in crystalline silicon

Based on first-principles density functional theory (DFT) calculations within the generalized gradient approximation (GGA), we propose a structural model for a diarsenic $({\mathrm{As}}_{s}\ensuremath{-}{\mathrm{As}}_{i})$ complex in Si and a mechanism for its reorientation, diffusion and dissociation. We find that the lowest-energy structure of ${\mathrm{As}}_{s}\ensuremath{-}{\mathrm{As}}_{i}$ consists of two As atoms bonded together in a single lattice site with a bond axis which is tilted slightly from the [110] direction. Our study demonstrates the ${\mathrm{As}}_{s}\ensuremath{-}{\mathrm{As}}_{i}$ pair may undergo reorientations within a lattice site and diffusion, with energy barriers of 1.05 and $1.33\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, respectively. Dissociation of an ${\mathrm{As}}_{s}\ensuremath{-}{\mathrm{As}}_{i}$ pair is likely to occur predominantly by the liberation of an $\mathrm{As}\ensuremath{-}{\mathrm{Si}}_{i}$ pair to leave behind a substititional As atom. The dissociation barrier is predicted to be $1.33\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, and the ${\mathrm{As}}_{s}\ensuremath{-}{\mathrm{As}}_{i}$ binding energy is calculated to be $1.00\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ relative to dissociation products ${\mathrm{As}}^{0}$ and $\mathrm{As}\mathrm{Si}_{i}{}^{0}$. We also discuss the role of ${\mathrm{As}}_{s}\ensuremath{-}{\mathrm{As}}_{i}$ pairs in As transient enhanced diffusion and clustering.

Ab InitioIdentification of the Nitrogen Diffusion Mechanism in Silicon

In this Letter, we present ab initio results identifying a new diffusion path for the nitrogen pair complex in silicon, resulting in an effective diffusivity of 67exp((-2.38 eV/kT) cm2/s. This nudged elastic band result is compared with other nitrogen diffusion paths and mechanisms, and is determined to have unmatched agreement with experimental results. It is also shown that careful consideration of total energy corrections and use of a fully temperature-dependent diffusion prefactor have modest but important effects on the calculation of diffusivity for paired and for interstitial nitrogen.

Vacancy-related complexes in neutron-irradiated silicon

Electrically active defects induced by neutron irradiation in n-type Czochralski-grown (Cz)Si crystals have been studied by means of capacitance transient techniques. Theseneutron-induced defects are compared with those created by electron irradiation andself-ion implantation. Four electron traps with the activation energies for electronemission of 0.12, 0.16, 0.24 and 0.42 eV were observed after neutron irradiation inphosphorous-doped Cz Si crystals. It is inferred that the E(0.12) and E(0.16) traps arerelated to the single-acceptor states of the silicon self-interstitial–oxygen dimer complex(IO2i) and the vacancy–oxygen pair (VO), respectively. The E(0.24) trap is associatedwith the electron emission from the double-acceptor state of the divacancy(V2). However, an asymmetric peak with its maximum at around 220 K and an activationenergy for electron emission of 0.42 eV dominated the spectra. We used high resolutionLaplace DLTS to investigate the structure of E(0.42) and found that this signal iscomplex, consisting of contributions from several defects. From the annealingbehaviour, it was revealed that as some of these defects anneal out they aresources of vacancies evidenced by an increase in the concentration of VO andV2. It is suggested that some of the defects contributing to the E(0.42) peak are related tosmall vacancy clusters.

Theory of boron-vacancy complexes in silicon

The substitutional boron-vacancy ${\mathrm{B}}_{s}\mathrm{V}$ complex in silicon is investigated using the local density functional theory. These theoretical results give an explanation of the experimentally reported, well established metastability of the boron-related defect observed in $p$-type silicon irradiated at low temperature and of the two hole transitions that are observed to be associated with one of the configurations of the metastable defect. ${\mathrm{B}}_{s}\mathrm{V}$ is found to have several stable configurations, depending on charge state. In the positive charge state the second nearest neighbor configuration with ${C}_{1}$ symmetry is almost degenerate with the second nearest neighbor configuration that has ${C}_{1h}$ symmetry since the bond reconstruction is weakened by the removal of electrons from the center. A third nearest neighbor configuration of ${\mathrm{B}}_{s}\mathrm{V}$ has the lowest energy in the negative charge state. An assignment of the three energy levels associated with ${\mathrm{B}}_{s}\mathrm{V}$ is made. The experimentally observed ${E}_{v}+0.31\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ and ${E}_{v}+0.37\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ levels are related to the donor levels of second nearest neighbor ${\mathrm{B}}_{s}\mathrm{V}$ with ${C}_{1}$ and ${C}_{1h}$ symmetry respectively. The observed ${E}_{v}+0.11\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ level is assigned to the vertical donor level of the third nearest neighbor configuration. The boron-divacancy complex ${\mathrm{B}}_{s}{\mathrm{V}}_{2}$ is also studied and is found to be stable with a binding energy between ${\mathrm{V}}_{2}$ and ${\mathrm{B}}_{s}$ of around $0.2\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. Its energy levels lie close to those of the ${\mathrm{V}}_{2}$. However, the defect is likely to be an important defect only in heavily doped material.

Diffusion and dissociation mechanisms of vacancy-oxygen complex in silicon

We are examining diffusion mechanisms of the vacancy-oxygen complex (VO) in bulk Si using ab initio calculations based on a 64-atom supercell. We found two atomic mechanisms involved in the VO diffusion; one is caused by migration of an interstitial oxygen atom, another by migration of a vacancy. The energy barrier of the mechanism due to an oxygen migration is 2.02eV, and that caused by a vacancy migration is 1.98eV. These energy barriers are close to the experimental activation energy of 2.0eV required for the dissociation and diffusion of VO. The derived activation energies of the two mechanisms suggest that these mechanisms plausibly occur simultaneously. In addition, we clarify that the dissociation energy of VO, 1.85eV, is lower than the diffusion energy of VO.

Analyses of images of neutron interactions and single particle displacement damage in CCD arrays

The purpose of this work is to understand the interaction of high energy neutrons with CCDs with the aim of deploying them in flight experiments to gather a database of atmospheric neutron interaction events in silicon cells. The new results in this paper include: 1) early-time multilevel RTS signals from dark current spikes, which have never been resolved before and 2) improved resolution of the frequency distributions of event intensity and comparison with results from a radiation transport code. This work adds to the state of the art by providing a novel perspective on the formation and evolution (annealing) of displacement damage complexes in silicon and by demonstrating that CCDs can provide an attractive combination of spatial and intensity resolution for the interaction events of neutrons and other particles within silicon cells.

Interaction between interstitials and arsenic-vacancy complexes in crystalline silicon

Using density functional theory calculations, we have examined the interaction of interstitials with various arsenic-vacancy complexes and compared these events to interstitial-vacancy (I-V) interactions. We find that the vacancy of AsmV(m=1–4) and AsmV2(m=2,3) complexes is easily annihilated by I-V recombination, with barriers of 0–0.08 eV and 0.16–0.21 eV, respectively, for the mono- and the di-vacancy associated complexes. The energy gain from the I-V recombination turns out to be significant (>1.3eV), implying that As would remain more favorably as Asn (or AsmIn) complexes, rather than as AsmVn in the presence of a large amount of excess interstitials. This suggests that interstitials may play an important role in As transient enhanced diffusion and agglomeration, especially at the early stage of postimplantation thermal annealing. We present the reaction paths and bonding mechanisms for the vacancy annihilation of Vn and AsmVn clusters by I-V recombination.

Annealing of vacancy complexes in P-doped silicon

In this paper we discuss possible mechanisms of PV and V2 annealing in Si. Our approach includes a combination of density functional theory and lattice kinetic Monte-Carlo (LKMC) simulations. The density functional theory is used to find the binding energies and jump barriers for P–V and V–V pairs at different separations (from one to three interatomic bonds between complex constituents) and in different charge states. The mobility and interaction of vacancies and vacancy complexes is simulated by LKMC with event probabilities calculated based on the energies from ab initio calculations.